They seem to be everywhere, and their numbers are expected to quadruple over the next four years. But many of them are untrustworthy, created just so your login credentials, to email or even more sensitive accounts, can be picked up by hackers using “sniffers” — software that captures any information you submit over the connection. The best defense against sniffing hackers is to use a VPN (virtual private network). A VPN keeps your private data protected because it encrypts what you input.

When your phone’s Wi-Fi is automatically enabled, you can be connected to an unsecure network without even realizing it. Use your phone’s location-based Wi-Fi feature, if it’s available. It will turn off your Wi-Fi when you’re away from your saved networks and will turn back on when you’re within range.

A firewall is your first line of defense against malicious intruders. It’s meant to let good traffic through your computer on a network and keep hackers and malware out. You should turn it off only when your antivirus software has its own firewall.

Sad to say, 55% of the Web’s top 1 million sites don’t offer encryption. An unencrypted website allows all data transmissions to be viewed by the prying eyes of hackers. Your browser will indicate when a site is secure (you’ll see a gray padlock with Mozilla Firefox, for example, and a green lock icon with Chrome). But even a secure website can’t protect you from sidejackers, who can steal the cookies from a website you visited, whether it’s a valid site or not, through a public network.

If you want to ensure that your own network is well protected, upgrade the firmware of your router. All you have to do is go to your router’s administration page to check. Normally, you can download the newest firmware right from the manufacturer’s site.

Needless to say, it is important to set up a password that is not too easy to guess, and change your connection’s default name. You can also filter your MAC address so your router will recognize only certain devices.

Josh Althuseris an open software advocate, Web architect and tech entrepreneur. Over the past 12 years, he has spent most of his time advocating for open-source software and managing teams and projects, as well as providing enterprise-level consultancy for Web applications and helping bring their products to the market. You may connect with him on Twitter.